[paho-dev] PAHO Embedded C library Transport Layer

[Veysel KARADAG <veyselka@xxxxxxxxxxx>]

Hi Every one ,

I'm trying to implement PAHO embedded C library to custom device ( STM32F405/GPRS module )

My main problem is create custom recv() function , which will use source for buffer.

In PAHO library example, there is a transport_getdata() function. It handle transportation layer. This is tranport_getdata() function.This example uses socket library from which I don't have :(

int transport_getdata(unsigned char* buf, int count)
{
    int rc = recv(mysock, buf, count, 0);
    //printf("received %d bytes count %d\n", rc, (int)count);
    return rc;
}

To port library to my project, I need to write my own recv() function like my_recv().

Standartd socket Recv() function description said,

Recv() will return length of message written to buffer from source.

So I try to write my_recv() for replace recv() , ( I don't need socket ID and FLAG)

int  my_recv(char *buf, int len){

    int i=0;

    if (len <= 0 )
        return -1;
    if (len > BUF_MAX)
        len=BUF_MAX - 2;

    for(i=0;i<len;i++){

        *buf=serial_buffer[0];
        *buf++;
        //shift one byte buffer to left
        memmove(serial_buffer, serial_buffer+1,(BUF_MAX-1)*sizeof(*serial_buffer));
        interrupt_pointer--; // After one byte shift, reduce serial interrupt pointer.
    }
    return i;
}

Handling TCP incoming data, I have a serial/TCP transparent connection over GPRS module.
I used interrupt to read every bytes . All incoming bytes written on serial_buffer.

void USART1_IRQHandler(void){

    int byte;

    if (USART_GetITStatus(USART1, USART_IT_RXNE) != RESET) // Received characters modify string
    {
            byte= USART_ReceiveData(USART1);

    }

    serial_buffer[interrupt_pointer]=byte;
    interrupt_pointer++;
    if(interrupt_pointer==BUF_MAX){
        interrupt_pointer=0;
        memset(serial_buffer,0,BUF_MAX);
    }

}

For simple test, I send "1234567890" from over TCP socket,

simple test code is

while(strlen(serial_buffer)>0){

    delay_ms(1000);
    printf("%s\r\n",serial_buffer);
    my_recv(buf,3);
    printf("%s\r\n",buf);
    printf("%s\r\n",serial_buffer);
}

My system out is,

1234567890 // All TCP data received
123        // getting 3 bytes from buffer
4567890    // remaining bytes

I'm not sure I understand recv() function well. Is this output is alright.

Couse still I cant handle MQTT package with PAHO library